The fastener cannot be generated. Remove this from the stack and proceed.
The part in brackets could be any fastener. Here's the sequence that causes it:
1. Insert fasteners using the standard parts database fastener system, into an assembly.
2. Modify the assembly structure in some way; for instance, I moved the locations of some subassemblies.
3. Open up the assembly with missing parts or subassemblies. Normally, I can then "replace" parts and find the missing files easily. But the fasteners are always missing.
4. Delete missing fasteners from the path finder.
5. Re-insert fasteners using the standard parts database fastener system. When I click "OK", I get this message.
Sometimes, I can fix the issue for some fasteners by finding the generated file, deleting it, and re-generating the fastener. This doesn't always work. Sometimes I can fix the issue by using the "update" feature of the Standard Parts Administrator. Again, it only works sometimes.
I'd like to know the root cause of the problem so I can resolve it consistently and without having to repeat myself or work-around every time it happens.